Shielding film and method for producing a shielding film

ABSTRACT

A shielding film for an apparatus with a device for wireless charging is provided which comprises several stacked layers. The layers each have several strips of a nanocrystalline soft magnetic alloy arranged on an adhesive layer, the nanocrystalline soft magnetic alloy having a round hysteresis loop. The strips of adjacent layers are offset with respect to one another.

This application is a 371 national phase entry of PCT/IB2013/060102,filed 13 Nov. 2013, which claims benefit of German Patent ApplicationNo. 10 2013 103 268.0, filed 2 Apr. 2013, the entire contents of whichare incorporated herein by reference for all purposes.

BACKGROUND

1. Field

The present disclosure relates to a shielding film, for example for anapparatus with a device for cordless charging, and a method formanufacturing a shielding film.

2. Description of Related Art

A cordless charging method, so-called “wireless charging,” is used tocharge the battery or accumulator of a mobile device without connectingthe mobile device to a power source via a mechanical connection such asa cable and/or plug.

US 2011/0241613 discloses a battery module with a resonator forwirelessly receiving power. A film is provided which serves to shieldagainst a magnetic field that is generated by the field-exciting coilsand produces eddy currents in the metallic parts of the battery, thusgenerating losses while the battery is being charged. The film can bearranged between the resonator and the battery. This film can have ahigh permeability and low losses in order to increase the shieldingperformance of the film. However, US 2011/0241613 does not discloses anyadditional features about this film, for example as pertains tocomposition or structure.

SUMMARY

The need therefore exists to provide shielding films that are suitablefor use in a wireless charging system.

A shielding film that is suitable for an apparatus with a device forcordless charging is provided which comprises several layers stacked oneon the other. The layers each have several strips of a nanocrystallinesoft magnetic alloy arranged on an adhesive layer. The nanocrystallinesoft magnetic alloy has a round hysteresis loop, and the strips ofadjacent layers are offset with respect to one another.

The shielding film is thus a composite of several layers, each of whichhas a soft magnetic layer with the strips and an adhesive layer. Theshielding film is also flexible if at least one of the soft magneticalloys and the adhesive layers is flexible and can thus be wrappedaround a component to be shielded and/or be adapted to the shape of thecomponent to be shielded.

In order to provide the shielding effect of the shielding film, thenanocrystalline soft magnetic alloy of the shielding film should havelow losses and consequently be of high quality. According to anembodiment of the invention, the nanocrystalline soft magnetic alloy hasa round hysteresis loop which increases the quality and reduces losses.

A round hysteresis loop is defined by a material with minimizedanisotropy, a remanence ratio Br/Bs of a permeability μ.

The round hysteresis loop of a nanocrystalline soft magnetic alloy iscreated through heat treatment without the conscious application of amagnetic field, i.e., only under the influence of the Earth's magneticfield or a mechanical tension.

The hysteresis loop has a remanence ratio Br/Bs in the closed magneticcircuit from 30% to 100%, an ideal round hysteresis loop having anisotopic remanence ratio of 100%. The hysteresis loop can be measured ona toroidal core having dimensions, for example, of outer diameterd_(a)=25 mm, inner diameter d_(i)=13 mm, and core height or band widthh=20 mm.

The permeability in the closed magnetic circuit measured, for example,on a toroidal core, is μ (1 A/m, 50 Hz)≥50,000, the permeability beingmeasured with a magnetic field=1 A/m and a measurement frequency=50 Hz.The toroidal core can have the dimensions: d_(a)=25 mm, d_(i)=13 mm,h=20 mm, for example, where d_(a) is the outer diameter, d_(i the) innerdiameter, h the core height or bandwidth.

For example, when manufacturing nanocrystalline band material on thecoil (of any bandwidths), test toroidal cores can also be includedduring heat treatment in order to determine the material characteristicof a round hysteresis loop on the test toroidal cores, which representsthe band material on the coil.

The quality is further increased by arranging several strips in a layerinstead of a continuous film made of a nanocrystalline soft magneticalloy. Through these separated strips, the eddy currents on the alloyplane can be spatially restricted, thus resulting in a domainrefinement. Moreover, the soft magnetic characteristics are isotropicdue to the round hysteresis loop, whereby magnetic fields from differentdirections can be shielded.

The strips of the nanocrystalline soft magnetic alloy of adjacent layersof the shielding film are offset with respect to one another. Inparticular, areas between the strips can be covered by a strip of theadjacent layer. This arrangement has the effect of improving the flowconductance from layer to layer and increasing the shieldingperformance.

This offset arrangement of the strips of adjacent layers of theshielding film can be provided in different ways. In one exemplaryembodiment, the strips of adjacent layers are arranged parallel andlaterally offset with respect to one another. In another exemplaryembodiment, the strips of adjacent layers are arranged transverse toeach other. In another exemplary embodiment, the strips of adjacentlayers are woven together. For example, the woven strips can runtransverse to each other and each have a wave shape.

The strips can have the shape of thin films or bands with a maximumthickness of 30 μm, for example. The strips can be manufactured using arapid solidification technique, for example.

Some nanocrystalline soft magnetic alloys are not ductile, but ratherare present in a brittle state, Examples of these alloys arenanocrystalline iron-based alloys such asFe_(73.8)Nb₃Cu₁Si_(15.6)B_(6.6), which are ductile in the amorphousstate but become brittle after heat treatment in order to improve thesoft magnetic characteristics. For these alloys, the adhesive layer canact as a substrate for the strips and impart a flexibility to theshielding film composite. If the adhesive layer is ductile, a flexibleshielding film is provided even though the shielding film materialitself, i.e., the strips of the nanocrystalline soft magnetic alloy, isbrittle.

The nanocrystalline soft magnetic alloy can be iron-based. In oneexemplary embodiment, the soft magnetic alloy consists of a compositionof Fe_(100-a-b-c-x-y-z)Cu_(a)M_(b)T_(c)Si_(x)Z_(z) and up to 0.5 atom %contaminants, where M is one or more of the group consisting of Nb, Moand Ta, T is one or more of the group consisting of V, Cr, Co and Ni,and Z is one or more of the group consisting of C, P and Ge, and 0.5atom %<a<1.5 atom %, 2 atom %≤b<4 atom %, 0 atom %≤c<5 atom %, 12 atom%<x<18 atom %, 5 atom %<y<12 atom % and 0 atom %≤z<2 atom %.

One example of this type of alloy is the nanocrystalline soft magneticalloy Fe_(73.8)Nb₃Cu₁Si_(15.6)B_(6.6), which is commercially availableunder the trade name VITROPERM® 800.

In one exemplary embodiment, the nanocrystalline soft magnetic alloy hasa hysteresis loop with a ratio of remanence induction, B_(r), oversaturation induction, B_(s), B_(r)/B_(s), in the closed magnetic circuitfrom 30% to 100%. The soft magnetic characteristics are thus even moreisotropic.

The nanocrystalline soft magnetic alloy has a frequency-dependentpermeability μ=μ′+iμ″ and a quality factor Q(f)=μ′/μ″. In one exemplaryembodiment, the maximum quality factor Q_(max)>20. This further reducesthe losses and further increases the shielding performance.

As already mentioned above, the strips can have the shape of a thin filmor of a band and can be manufactured using rapid solidificationtechnology, for example. The quality increases as the thicknessesdecrease. In one exemplary embodiment, the strips have a thickness, d,where d≤22 μm. In one exemplary embodiment, the strips have a thicknessof 18 μm±3 μm.

In one exemplary embodiment, adjacent strips of a layer are spaced apartfrom one another by 0.1 mm to 0.3 mm. If the spacing is kept small, thedensity of the soft magnetic alloy and the flow conductance can beincreased.

The adhesive layer can a self-supporting adhesive film that is adhesiveon one or both sides. The adhesive layer can also be applied to thestrips in liquid form or as a powder.

In one exemplary embodiment, an adhesive film is arranged between thestrips of adjacent layers. The adhesive film can act as a substrate forthe strips and can be present instead of or in addition to the adhesivelayer. This film can be adhesive on both sides. The uppermost and/orlowermost layer of the shielding film can also be covered by an adhesivefilm. This adhesive film can act as a protective film and/or as anadhesive surface.

An object with a battery, a receiver for the wireless reception ofpower, and a shielding film according to any one of the precedingexemplary embodiments is also provided. The object can be a portablemobile device, such as a cell phone, whose battery must be rechargedover and over again. A battery is understood as an accumulator that canbe recharged by an external power source.

The shielding film can be arranged in various places in the object. Forexample, the shielding film can be arranged between the battery and thereceiver or around electronic components of the object.

If the object further comprises a housing with an inner surface, theshielding film can be arranged on the inner surface. For example, theshielding film can be arranged on the inner surface such that electroniccomponents of the device are shielded against an external magneticfield.

If the shielding film is flexible, it can be wound around surfaces to beshielded and/or adapted thereto.

The shielding film can also be arranged in the second part of thewireless charging system. An object is thus provided which comprises atransmitter for the wireless transmission of power to a receiver and ashielding film according to any one of the preceding exemplaryembodiments. This object is typically connected mechanically to a powersource.

The shielding film can be arranged on the transmitter or on an innersurface of a housing of the object.

The receiver and the transmitter can have different shapes. For example,the receiver and/or the transmitter can have a resonant circuit and/or acoil.

A method for manufacturing a shielding film is also provided whichcomprises the following: A band of an amorphous soft magnetic alloy isreadied. The band is heat-treated at a temperature of 500° C. to 600° C.from 1 minute to 1 hour under an N₂- or H₂-containing atmosphere andunder the Earth's magnetic field, a nanocrystalline soft magnetic bandbeing created with a round hysteresis loop. An adhesive layer is appliedto at least one side of the band, thus creating a layer. The band isstructured so as to produce several strips from the band. At least twolayers are stacked one on top of the other, so that the strips ofadjacent layers are offset with respect to one another, thus creating ashielding film.

A shielding film can also consist of one layer of the cut strips, thestrips being held together by an adhesive film.

To increase the soft magnetic characteristics, the band is heat-treatedat a temperature of 500° C. to 600° C. from 1 minute to 1 hour under anN₂- or H₂-containing atmosphere. An additional external magnetic fieldis not applied during the heat treatment, so that the heat treatmentoccurs only under the influence of the Earth's magnetic field in orderto produce a round hysteresis loop in the band.

Different sequences of some of these steps can be used. In one exemplaryembodiment, the amorphous band is first applied to a substrate and thenheat-treated, upon which an adhesive film is applied to thenanocrystalline band. The band is then structured so as to produceseveral strips from the nanocrystalline soft magnetic alloy on theadhesive layer.

In an alternative exemplary embodiment, the amorphous band is structuredso as to produce several strips, upon which the strips are heat-treatedin order to produce the nanocrystalline soft magnetic alloy, and then anadhesive film is applied to the strips.

In another exemplary embodiment, amorphous bands are woven together andthen heat-treated. These bands can also be strips that are cut from anamorphous band like in the previous exemplary embodiment.

A one-sided or two-sided adhesive film or heat-sealable film or powderedhot glue can be used as the adhesive layer. Two or more differentmaterials for different adhesive layers can be used in a shielding film.

The heat treatment can be done in a continuous pass. This method can beused in the case of a woven structure or in a step sequence in which theband or the strips are heat-treated.

The band can be structured using various methods in order to produce thestrips. For example, the band can be cut mechanically or chemically intoseveral strips. The band can be cut mechanically into several stripsusing rolling scissors or pulled against a sharp edge under tensileforce in order to divide the band into several parts or fragments. Theseseveral parts or fragments act as several strips.

In another exemplary embodiment, shielding parts are punched or cut fromthe band with an amorphous alloy or from the band with a nanocrystallinealloy.

These shielding parts can then be stacked one on top of the other inorder to produce a multilayer shielding film. In the case of shieldedparts of an amorphous alloy, the parts can be stacked before or afterthe heat treatment.

The use of a shielding film according to any one of the precedingexemplary embodiments in an object with components for wireless chargingis also provided. Components for wireless charging can be a coil and/ora resonator circuit, for example.

Moreover, the shielding film according to any one of the precedingexemplary embodiments can be used in an object with components to beshielded. Components to be shielded can be prone to failure under theinfluence of an external magnetic field. For example, the components tobe shielded can be one or more of the group consisting of electroniccomponents, cables, sensor regions and hollow spaces.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments and certain examples will now be explained infurther detail with reference to the drawings and table.

FIG. 1 shows a schematic representation of a wireless charging system,

FIG. 2a shows a top view of a layer of a shielding film,

FIG. 2b shows a cross section of the layer of the shielding film of FIG.2 a,

FIG. 2c shows a cross section of a layer of a shielding film with anadditional adhesive layer,

FIG. 3 shows a cross section of a layer of a shielding film with severallayers according to a first exemplary embodiment,

FIG. 4a shows a cross section of a layer of a shielding film accordingto a second exemplary embodiment,

FIG. 4b shows a perspective view of the layers of the shielding film ofFIG. 3 a,

FIG. 5 shows a schematic representation of a shielding film according toa third exemplary embodiment,

FIG. 6 shows a schematic view of the experimental setup for performingfrequency-dependent quality measurements on flat, round specimens,

FIG. 7 shows a schematic view of an experimental setup for performingfrequency-dependent quality measurements,

FIG. 8 shows diagrams of quality as a function of frequency forspecimens with different hysteresis loops,

FIG. 9 shows a diagram of quality as a function of frequency forspecimens of different thickness,

FIG. 10 shows diagrams of quality as a function of frequency forspecimens of different thickness,

FIG. 11 shows a schematic representation of the induced anisotropy in asquare specimen on a planar inductor,

FIG. 12 shows a diagram of quality as a function of frequency for aspecimen with an adhesive film, and

FIG. 13 shows a diagram of quality as a function of frequency for ashielding film with several strips of a nanocrystalline soft magneticalloy.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1 shows a schematic representation of a system 10 for the cordlesscharging—“wireless charging”—of a device 13. The system 10 has a firstpart 11 with a transmitter coil 12 for transmitting power to a separatedevice 13, for example a mobile or portable device such as a cell phonehaving a receiver coil 14 for receiving power.

The first part 11 is connected to a power source, for example via acable and plug. The power that is transmitted wirelessly from thetransmitter coil 12 of the first part 11 to the receiver coil 15 in theseparate device 13 is used there to charge a battery or accumulator (notshown).

The mobile device 13 has a shielding film 15 that shields against thepenetration of the magnetic field into the device 13 or into electroniccomponents of the device 13. The shielding film can be arranged on theinterior of the device 13 and/or between the coil and the battery to becharged. Two or more shielding films can be integrated into the device13. One or more shielding films 15 can also be integrated into the firstpart 11.

FIG. 2a shows a top view and FIG. 2b a cross section of a layer 20 of ashielding film according to a first exemplary embodiment that can beused as a shielding film in a wireless charging system. The layer 20 hasseveral strips 22 of a nanocrystalline soft magnetic alloy. In thisexemplary embodiment, this alloy is an iron-based alloy and particularlyFe_(73.8)Nb₃Cu₁Si_(15.6)B_(6.6). The strips 22 are arranged parallel toone another and on an adhesive layer 24, which is a one-sided adhesivefilm in this exemplary embodiment. The adhesive film acts as a substratefor the strips 22. The strips 22 are arranged on a plane and separatedfrom one another by gaps 26 that are bridged over by the adhesive layer24.

FIG. 2c shows a layer 30 according to a second exemplary embodiment fora shielding film. The layer 30 has a plurality of strips 31 of ananocrystalline soft magnetic alloy that are also arranged on anadhesive layer 32. The layer 30 has an additional adhesive layer 33 thatis arranged on the upper sides 34 of the strips 31, so that the strips31 are arranged between two adhesive layers 32, 33. In this exemplaryembodiment, the gaps 35 between the strips 31 are not covered by thesecond adhesive layer 32, and these areas of the adhesive layer 32 aretherefore open.

FIG. 3 shows a cross section of a shielding film 40 according to a firstexemplary embodiment. The shielding film 40 has three layers 41, 42, 43,each of which has a plurality of parallel strips 44, 44′, 44″ of ananocrystalline soft magnetic alloy and at least one adhesive layer 45.The lowermost layer 41 has a continuous adhesive film 45 that forms anouter surface of the shielding film 40.

A plurality of strips 44 are arranged on this adhesive film 45. A secondadhesive layer 46 is arranged on the upper sides 47 of the strips 44.

The second layer 42 has a plurality of strips 44′ that are also arrangedparallel to each other on a plane. The strips are arranged on the secondadhesive layer 46 of the first layer 41, the strips 44′ of the secondlayer 42 being offset laterally in relation to the strips 44 of thefirst layer 41, so that an area of the strip 44′ of the second layer 42covers the gaps between the strips 44 of the first layer 41. The secondlayer 42 also has an adhesive layer 46, which is arranged on the uppersides 47 of the strips 44′.

Like the other two layers 41, 42, the third layer 43 of the shieldingfilm 40 has a plurality of parallel strips 44″ on whose upper side 47 anadhesive layer 48 is arranged. The strips 44″ of the third layer 43 arearranged on the adhesive layer 46 of the second layer 42, so that thestrips 44″ of the third layer 43 are offset laterally in relation to thestrips 44′ of the second layer 42. The strips 44″ of the third layer 43are not offset laterally in relation to the strips 44 of the first layer42. The strips 44, 44′, 44″ of the three layers 41, 42, 43 run parallelto each other. A second outer adhesive film 49 is arranged on theadhesive layer 48 of the third layer 43, so that the strips 44, 44′, 44″of the three layers 41, 42, 43 are arranged between two adhesive films45, 49.

FIG. 4a shows a cross section and FIG. 4b a perspective view of ashielding film 50 according to a second exemplary embodiment. Theshielding film 50 has two layers 51, 52, each layer 51, 52 having aplurality of parallel strips 53, 54 of a nanocrystalline soft magneticalloy that are arranged on an adhesive film 55, 56. The strips 53 of thelower layer 51 further comprise an adhesive layer 57 on its upper sides58. The strips 54 of the upper layer 52 are arranged transverse to thestrips 53 of the first layer 51, so that the strips 54 of the upperlayer 52 bridge over the gaps 59 between the strips 53 of the lowerlayer 51, and the strips 53 of the lower layer 51 bridge over the gaps59 between the strips 54 of the upper layer 52. The two adhesive films55, 56 form the outer surface of the shielding film 50. The adhesivelayer 57 is thus arranged between the strips 53, 54 and between thelayers 51, 52 of the shielding film 50.

FIG. 5 shows a shielding film 60 according to a third exemplaryembodiment. The shielding film 60 has two layers 61, 62, each of whichhas a plurality of strips 63, 64 of a nanocrystalline soft magneticalloy and an adhesive layer 65, 66, the adhesive layer 65, 66 beingarranged on a side 67 of the strips 63, 64. In this exemplaryembodiment, the strips 63, 64 of the two layers 61, 62 run transverse toeach other and are woven together in order to produce a woven structurein which each strip 63, 64 is wave-shaped.

To increase the shielding performance, the soft magnetic alloy shouldhave the following characteristics: a high permeability, as little lossas possible in the frequency range>100 kHz, and as high a quality factoras possible in the frequency range>100 kHz.

Below, quality measurements performed on planar inductors are described.On the basis of the exemplary embodiments, selections can be made interms of material, band thickness, heat treatment method andstructuring. The heat treatment of the specimens was performed on astack of about 50 individual parts. For the examples, the VITROVAC®alloys VC 6025 I50, VC 6155 U55 with the compositionFe_(69.5)Nb_(3.5)Mo₃Si₁₆B₇ and Co_(72.7)Fe_(4.8)Si_(5.5)B₁₇,respectively, and the VITROPERM® alloy VP 800 with the compositionFe_(73.8)Nb₃Cu₁Si_(15.6)B_(6.6) were used.

The material quality measurements were carried out with the aid of aplanar coil and an LC measuring bridge. The square or round specimenswere placed at a minimal distance (e.g., about 0.2 to 0.3 mm) to oneside of the planar coil. All of the results shown subsequently relate toa single material layer. Depending on the application, however, ashielding film or a shielding part can have several soft magneticlayers.

FIG. 6 shows a schematic view of the experimental setup for thefrequency-dependent quality measurement on flat, round specimens.

FIG. 7 shows a schematic view of an experimental setup for thefrequency-dependent quality measurement on flat, square specimens (top)and on flat, square specimens with inner structuring in order to producestrips from the specimen. The strips have a strip width of 1 mm, adistance between the strips of 0.2 mm and can be produced throughlaser-cutting using a Q-switch laser, for example, or through cuttingwith rolling scissors, for instance, into strips and subsequentassembly.

FIGS. 6 and 7 show the experimental setup for determining thefrequency-dependent quality. An LC measuring bridge is used to determinethe frequency-dependent complex permeability μ=μ′+μ″ of a planarinductor. The inductor is composed of the coil and the placed specimen.The quality factor is calculated from:Q(f)=μ′/μ″and since the cycle losses due to eddy currents are determined only fromthe imaginary part of the permeability, a high quality factor isobtained in those frequency ranges in which the material losses aresmall.

The influence of the alloy system on the quality was examined.

FIG. 8 shows diagrams of quality as a function of frequency. Thefrequency-dependent quality was measured on specimens having a geometryof 20.3×20.3 cm. The results for Co-based alloys such as VC 6025 50 andVC 6155 U55 are shown on the left side, and results for themonocrystalline Fe-based alloy VP 800 are indicated on the right side.For both material classes, the specimens are present after a heattreatment without a magnetic field, which are designated by X, and witha magnetic field, which are designated by F and Z.

The material parameters, the heat treatment status and the maximumachievable quality values are summarized in table 1 for the illustratedexamples. By comparing the maximum achievable quality values, one cansee that higher quality values can be achieved with Fe-based alloys inthe nanocrystalline state.

FIG. 9 shows a diagram of quality as a function of frequency for sampleshaving a geometry d_(a)=28 mm d_(i)=10 mm of the Co-based alloy VC 602550 with different band thicknesses in the range from 15 μm to 34 μm.

FIG. 10 shows diagrams quality as a function of frequency. Thefrequency-dependent quality was measured on specimens having a geometryof 20.3 mm×20.3 mm with different band thicknesses for the alloys VC6025 50 and the alloy VP800 in the nanocrystalline state. The bandthickness of the specimens was 15 μm and 27 μm, and a heat treatment wasused that is suitable for producing a round hysteresis loop.

The eddy current losses are reduced with increasing material thickness.Accordingly, the highest quality values are achieved in the smallestband thicknesses, as can be seen from FIG. 8, FIG. 10 and from table 1.

The influence of the heat treatment with and without magnetic field onthe quality was investigated.

Heat treatment of the materials cited above can be performed with andwithout the application of magnetic fields. Through the application ofmagnetic fields during a heat treatment, aligned anisotropes can beintroduced into soft magnetic specimens. A heat treatment without amagnetic field yields specimens with round hysteresis loops having onlya very small residual anisotropy. These samples are designated by theletter “X.”

If a magnetic field is applied during heat treatment transverse to theband longitudinal direction, a transverse anisotropy is obtained in thespecimen, which leads, when measured in the band direction, to a “flat”hysteresis loop that is designated by the letter “F.”

Likewise, it is possible to apply the magnetic field parallel to theband longitudinal direction during the heat treatment. In that case, oneobtains a longitudinal anisotropy in the specimen, which leads, whenmeasured in the band direction, to a “Z-shaped” hysteresis loop. Thesesamples are designated by the letter “Z.”

One would now expect for specimens with “flat” hysteresis loops toexhibit good quality, since toroidal cores with “flat” hysteresis loopshave less loss. It can be seen from FIG. 6 and table 1, however, thatspecimens with “round” hysteresis loops (X) have substantially higherquality values than specimens with “flat” hysteresis loops (F). Anexplanation of this is given in FIG. 9. In the square specimen, theradially symmetrical magnetic field of a planar coil leads to areas with“flat” hysteresis (direction of anisotropy normal to the field line(.L)) and to areas with “Z-shaped” hysteresis loops (direction ofanisotropy parallel to the field line (II)). Both areas occur in thespecimens.

FIG. 11 shows a schematic representation of the induced anisotropy(transverse, longitudinal) in a square specimen on a planar inductor. Inboth cases, there are areas in which the induced anisotropy is alignedparallel (| |) and in which the anisotropy is aligned normal to themagnetic field profile in the specimen.

Toroidal cores with “Z-shaped” hysteresis loops exhibit high losses. Dueto the mixed state, planar specimens with an “F” or “Z” heat treatmentare therefore more prone to losses and thus exhibit lower quality. Inthe case of square specimens (here 20.3×20.3 mm) that are used in aradially symmetrical coil arrangement (see FIG. 9), there is nodistinction between specimens with longitudinal (Z) and transverseanisotropy (F).

As shown in the exemplary embodiment in table 1, the best qualityfactors are obtained for nanocrystalline Fe-based alloys such asVITROPERM® 800 after heat treatment on a “round” hysteresis loop.

The influence of a coating with adhesive film on the quality wasexamined.

FIG. 12 shows a diagram of the quality as a function of frequency. Thefrequency-dependent quality was measured on specimens with a geometry of20.3×20.3 mm of the alloy VP800 in the nanocrystalline state with heattreatment on “round” hysteresis loops. The illustration shows ameasurement on an uncoated specimen and on a specimen coated with anadhesive film. The band thickness of both specimens is 17 μm.

The influence of the coating of nanocrystalline VITROPERM® 800 specimenswith adhesive band on the quality is low. Indeed, measurements of thequality profile on coated and uncoated specimens yielded very similarvalues, as can be seen from FIG. 10. The results have also beenpresented in table 1. This result is useful, since the innerstructuring, for example by cutting the material on rolling scissors andsubsequent joining, is only possible after coating of thenanocrystalline material with an adhesive film.

The influence of the inner structuring on the quality was alsoinvestigated.

Another increase in quality with nanocrystalline VITROPERM® 800 with“round” hysteresis loop was also achieved through inner structuring. Forthis purpose, narrow slits were introduced in the material plane. FIG.10 shows a comparison of the quality profile for a nanocrystallinespecimen with and without inner structuring, and that the quality can bedoubled through inner structuring. The material parameters, the heattreatment status, and the quality values achieved for the individualspecimens have been summarized in table 1. The reduction in losses canbe explained on the one hand by the interruption of the eddy currents onthe alloy plane and on the other hand by the resulting domain refinementin comparison to non-slitted specimens. The domain refinement wasconfirmed using a Kerr microscope.

FIG. 13 shows a diagram of the quality as a function of frequency. Thefrequency-dependent quality was measured on a sample with the geometry20.3×20.3 mm of the alloy VP800 in the nanocrystalline state with heattreatment on a “round” hysteresis loop. The quality profile of thespecimen was first measured in the undivided state. The specimen wasthen measured after it was divided into 2, 4, 8 and 16 parts,respectively. This corresponds to structures of 10.2 mm, 5.1 mm, 2.5 mmand 1.3 mm with spacing between the individual parts of 0.2 mm. Thequality profile was then measured again.

The material parameters, the heat treatment status and the qualityvalues achieved for the individual structures are summarized in table 1.FIG. 13 shows further influence of the strip width on the quality. Thequality value increases as the strip width decreases. In order toachieve an efficient increase in quality, the strips of the innerstructuring must be selected so as to be as narrow as possible.

To produce single-layer or multilayer shielding films or shielding partswith high quality from a nanocrystalline, soft magnetic Fe-based alloy(VITROPERM® 800), one of the following production methods can be used.

1.) Heat treatment on the coil=>film composite=>structure=>shieldingfilm or shielding part

Using this production method, the individual processes can be carriedout very cost-effectively. The starting point is represented by adirectly cast or cut VITROPERM® band of any width wrapped into coils onspecial substrates. The coils are then heat-treated on a “round”hysteresis loop at 575° C. and under N₂ or H₂ atmosphere, the materialbeing brought to the nanocrystalline state. The brittle band is nowcoated with an adhesive band in a “reel-to-reel,” i.e., coil-to-coilprocess in order to ensure workability for ensuing steps. For amultilayer film composite (several layers of VITROPERM®), thereel-to-reel process must be carried out several times with double-sidedadhesive band. By virtue of the coating with adhesive band, theotherwise brittle band material can now be subjected to additionalprocessing steps. Shielding parts can then be manufactured directly bycutting or punching.

For shielding material that meets higher quality demands, internalstructuring can be performed. The single-layer or multilayer filmcomposite is now cut on rolling scissors into narrow strips (0.5 to 10mm). A device is used to bring the individual strips together again onanother substrate adhesive band with mutual spacing of <0.2 mm, thusresulting in a film composite as shown in FIG. 3.

For a multilayer, structured construction with offset stacking,single-layer composite films can be cut into narrow strips and broughttogether again. The resulting structured films can then be broughttogether in an offset manner as shown in FIG. 3. A similar procedure isproposed for the manufacture of cross-stacked shielding films (see FIG.4).

2.) Part=>structure=>heat treatment on the part=>filmcomposite=>shielding part

The production process described under 1.) provides for the mechanicalprocessing of the material after heat treatment in a “reel-to-reel”process in which the individual shielding part is created only at theend of the production chain. In contrast to that, the heat treatment canbe performed on parts that have already been prefabricated, stackedpackets and structured stacked packets.

For this purpose, directly cast or cut VITROPERM® band of any width isprocessed. The manufacture of individual parts could be done on rollingscissors, automatic cutting machines or punches. This is followed by theheat treatment of the individual parts on a “round” hysteresis loop at575° C. and under N₂ or H₂ atmosphere, the material being brought intothe nanocrystalline state. The brittle individual parts are then coatedor brought together into packets stacked in a structured manner, all ofthe possibilities described under 1.) being possible. A flexibleshielding part is obtained by coating the heat-treated parts, thestacked packets or the structure-stacked packets with adhesive film.This adhesive film should preferably be present as a long substrate filmin order to enable a subsequent reel-to-reel process.

3.) Woven fabric of VITROPERM® bands=>heat treatment=>filmcomposite=>shielding film

The starting point is represented here by a woven fabric, e.g., tubeweave, of narrowly cut VITROPERM® band (see FIG. 5), the bands having awidth of 0.5 to 0.6 mm, for example. The flat-lying woven fabric issubjected to heat treatment on a “round” hysteresis loop at 575° C.under N₂ or H₂ atmosphere, the material being brought into thenanocrystalline state. The now-brittle woven fabric of nanocrystallinebands is now coated while lying flat in a device with an adhesive bandin order to ensure workability for ensuing steps.

For a multilayer film composite, the reel-to-reel process can be carriedout several times with double-sided adhesive band. This method has theadvantage that the inner structuring is already present in the form ofthe weave, whereby the losses are again greatly reduced and resultinghere, too, in shielding material of high quality.

4.) Heat treatment on the coil=>film composite=>structure throughbreaking=>shielding film

The starting point is represented by a directly cast or cut VITROPERM®band wrapped into coils on special substrates. The coils are thenheat-treated on a “round” hysteresis loop at 575° C. and under N₂ or H₂atmosphere, the material being brought to the nanocrystalline state. Thebrittle band is now coated on both sides with an adhesive band in a“reel-to-reel” process. To increase the quality, another procedure forinner structuring is proposed here. In the described reel-to-reelprocess, the film composite must be pulled under tensile force over asharp metal edge in order to break the brittle VITROPERM® band locatedbetween the films into small parts. Here, too, the eddy currents on thematerial plane are spatially limited, the losses are reduced and thequality factor is increased.

Further processing into multilayer shielding films or parts would bepossible in a manner analogous to that described under 1.).

Instead of the abovementioned commercially available one-sided ordouble-sided adhesive films, which are necessary for fixing the layersof magnetic material or to achieve inner structuring, other adhesivetechnologies such as heat-sealable films, powdered hot adhesives or thelike can be used.

TABLE 1 Js Thickness Inner Quality Frequency at No. Material [T] d [μm]Heat treatment² structure Q_(max) [ ] Q_(max) f [kHz] 1 VC 6155 U55 0.9923 F, Z, amorphous none 11.5 70 2 VC 6025 I50 0.55 34 F, Z, amorphousnone 11.0 80 3 VC 6025 I50 0.55 27 F, Z, amorphous none 12.3 90 4 VC6025 I50 0.55 23 F, Z, amorphous none 12.9 100 5 VC 6025 I50 0.55 20 F,Z, amorphous none 13.6 106 6 VC 6025 I50 0.55 15 F, Z, amorphous none14.2 112 7 VC 6025 I50 0.55 27 X, amorphous none 17.5 100 8 VC 6025 I500.55 15 X, amorphous none 22.2 130 9 VC 6025 I50 + 0.55 27 X, amorphous29.9 130 KF³⁾ 10 VP 800 1.21 17 F, Z, nano none 15.8 100 11 VP 800 1.2125 X, nano none 26.2 170 12 VP 800 1.21 17 X, nano none 35.5 350 13 VP800 + KF³⁾ 1.21 17 X, nano none 35.9 360 14 VP 800 + KF³⁾ 1.21 17 X,nano 10.2 mm  41.1 410 0.2 mm 15 VP 800 + KF³⁾ 1.21 17 X, nano 5.1 mm49.2 510 0.2 mm 1 VP 800 + KF³⁾ 1.21 17 X, nano 2.5 mm 54.2 630 0.2 mm 1VP 800 + KF³⁾ 1.21 17 X, nano 1.3 mm 59.2 770 0.2 mm

Numbers 1 to 7 and 10 show comparative examples for the related art,while numbers 8, 9 and 11 to 17 show examples according to an embodimentof the invention.

Terms used in the table:

-   1) J_(s): saturation polarization-   2) Heat treatment:    -   X—Heat treatment without magnetic field    -   F—Heat treatment in the magnetic transverse field with the        result of anisotropy transverse to the band longitudinal        direction    -   Z—Heat treatment in the magnetic longitudinal field with the        result of anisotropy along the band longitudinal direction    -   Amorphous—After treatment, the specimen is present in the        amorphous state    -   Nano—After treatment, the specimen is present in the        nanocrystalline state        and-   3) KF: Laminated with adhesive film

The invention claimed is:
 1. A shielding film for a device withcomponents for wireless charging, comprising: a plurality of stackedlayers, wherein the layers each have a plurality of strips of ananocrystalline soft magnetic alloy arranged on an adhesive layer, thenanocrystalline soft magnetic alloy having a round hysteresis loop andthe strips of adjacent layers being offset with respect to one another,and wherein the nanocrystalline soft magnetic alloy has a hysteresisloop with a ratio of remanence induction, Br, to saturation induction,Bs, Br/Bs, in the closed magnetic circuit from 30% to 100%.
 2. Theshielding film as set forth in claim 1, wherein the soft magnetic alloyconsists of a composition of Fe100-a-b-c-x-y-zCuaMbTcSixZz and up to 0.5atom % contaminants, where M is one or more of the group consisting ofNb, Mo and Ta; T is one or more elements selected from the groupconsisting of V, Cr, Co and Ni; and Z is one or more elements selectedfrom the group consisting of C, P and Ge; and wherein 0.5 atom % <a<1.5atom %, 2 atom % <b<4 atom %, 0 atom % <c<5 atom %, 12 atom % <x<18 atom%, 5 atom % <y<12 atom % and 0 atom % <z<2 atom %.
 3. The shielding filmas set forth in claim 1, wherein the nanocrystalline soft magnetic alloyis Fe_(73.8)Nb₃Cu₁Si_(15.6)B_(6.6).
 4. The shielding film as set forthin claim 1, wherein the shielding film is capable of being wound aroundsurfaces and/or adapted to surfaces.
 5. The shielding film as set forthin claim 1, wherein the strips have the structure of a film or of aband.
 6. The shielding film as set forth in claim 1, wherein thenanocrystalline soft magnetic alloy has a frequency-dependentpermeability μ=μ′+iμ″ and a quality factor Q(f)=μ′+μ″, such that themaximum quality factor Qmax is >22.
 7. The shielding film as set forthin claim 1, wherein the strips have a thickness d, where d <20 μm. 8.The shielding film as set forth in claim 1, wherein adjacent strips of alayer are spaced apart from one another by a gap of 0.1 mm to 0.3 mm. 9.The shielding film as set forth in claim 1, wherein an adhesive film isarranged between the strips of adjacent layers.
 10. The shielding filmas set forth in claim 1, wherein strips of adjacent layers are arrangedparallel to one another.
 11. The shielding film as set forth in claim 1,wherein the strips of adjacent layers are arranged transverse to oneanother.
 12. A shielding film for a device with components for wirelesscharging, comprising: a plurality of stacked layers, wherein the layerseach have a plurality of strips of a nanocrystalline soft magnetic alloyarranged on an adhesive layer, the nanocrystalline soft magnetic alloyhaving a round hysteresis loop and the strips of adjacent layers beingoffset with respect to one another, and wherein the strips of adjacentlayers are interwoven.
 13. An object comprising a battery, a receivercoil for wirelessly receiving power, and a shielding film as set forthin claim
 1. 14. The object as set forth in claim 13, wherein theshielding film is arranged between the battery and the receiver coil.15. The object as set forth in claim 13, wherein the object furthercomprises a housing with an inner surface, and wherein the shieldingfilm is arranged on the inner surface.
 16. An object comprising atransmitter coil for wirelessly sending power to a receiver coil, and ashielding film as set forth in claim
 1. 17. The object as set forth inclaim 16, wherein the shielding film is arranged on the transmittercoil.
 18. The object as set forth in claim 16, wherein the objectfurther comprises a housing with an inner surface, and wherein theshielding film is arranged on the inner surface.
 19. A method formanufacturing a shielding film, comprising the following: providing aband of an amorphous soft magnetic alloy thermally treating the band ata temperature of 500° C. to 600° C. for 1 minute to 1 hour under an N2-or H2-containing atmosphere and under the Earth's magnetic field,thereby creating a nanocrystalline soft magnetic band with a roundhysteresis loop, applying an adhesive layer to at least one side of theband, thus creating a layer, structuring of the band in order to produceseveral strips from the band, stacking of at least two layers on oneanother, so that the strips of adjacent layers are offset with respectto one another, thus creating a shielding film according to claim
 1. 20.The method as set forth in claim 19, wherein the band is first appliedto a substrate, then thermally treated, after which an adhesive film isapplied to the band and, finally, the band is structured in order toproduce several strips on the adhesive film.
 21. The method as set forthin claim 19, wherein the amorphous band is structured in order toproduce several strips, then thermally treated, after which an adhesivefilm is applied to the strips.
 22. The method as set forth in claim 19,wherein amorphous bands are interwoven and then thermally treated. 23.The method as set forth in claim 19, wherein a one-sided or double-sided adhesive film, heat-sealable film or powdered hot adhesive is usedas the adhesive layer.
 24. The method as set forth in claim 19, whereinthe thermal treatment is done in a continuous pass.
 25. The method asset forth in claim 19, wherein the band is cut mechanically orchemically into several strips.
 26. The method as set forth in claim 19,wherein the band is cut mechanically with rolling scissors into severalstrips.
 27. The method as set forth in claim 19, wherein the band ispulled under tensile force over a sharp edge in order to divide the bandinto several parts.
 28. The method as set forth in claim 19, whereinshielding parts are punched or cut from the band with an amorphous alloyor from the band with a nanocrystalline alloy.
 29. A method of shieldingan object with components for wireless charging comprising applying tothe object a shielding film as set forth in claim
 1. 30. A method ofshielding an object with components to be shielded comprising applyingto the object a shielding film as set forth in claim
 1. 31. The methodas set forth in claim 30, wherein the components to be shielded includeone or more of the group consisting of electronic components, cables,sensor regions, and hollow spaces.